Interaction of synthetic human big gastrin with blood proteins of man and animals.

Radio gel and affin chromatography were used to study big gastrin interaction with blood proteins of man and animals. The experiments showed that big gastrin interacts with serum proteins in vitro. The gastrin-blood protein complex is labile and readily dissociates (T 1/2 = 8--14 min). A more stable complex is found in acidic medium. Ceruloplasmin is one of the blood serum proteins able to interact with big gastrin. The stability of hormone-protein complex, formed by gastrin and ceruloplasmin, is dependent upon hormone concentration. With the addition of C-terminal penta--and octapeptides to labelled hormone, binding increased. It is speculated that formation of labile gastrin-blood protein complexes is necessary for selective gastrin transport from hormone-producing cells to target cells.